This invention relates to sealing of cables. More particularly, this invention relates to wrap-around cable sleeves.
In the electrical utilities industry, maintaining cable integrity may be critical. A loss of cable integrity, for example, a short circuit in a high voltage cable, may result in a crippling power outage, or, even worse, a loss of life. One everyday task that may pose a great threat to cable integrity is the formation of electrical connections.
When electrical connections are formed, a bare metal surface may be exposed such as a splice connector. These bare metal surfaces may be particularly hazardous when formed in the field where they are exposed to the environment. This environment may include rocks and other sharp objects as well as moisture when the connection is to be buried under ground and rainfall when the connection is to be suspended in the air. Thus, there is a need to protect such electrical connections from the environment.
U.S. Pat. No. 5,828,005 to Huynh-Ba et al. proposes the use of a gel-filled closure for environmentally protecting a connector forming a connection between a cable and at least one electrical component. The closure may include first and second cavitied bodies, each having two lateral sides and two end sides. The closure may have a hinge joining the first and second bodies along a lateral edge. The closure may be integrally made of a thermoplastic material by injection molding. The thermoplastic material may have a tensile yield strength of at least 3,500 pounds per square inch (psi). The closure may include reinforcing ribs that decrease the deflection in the closure near fingers as the enclosed gel expands during service at elevated temperatures.
While the gel may protect the connection from moisture and the closure may provide protection from rocks and other buried sharp objects, such a solution may ultimately be less than optimal. The reinforcing ribs may need to be designed to withstand a given internal pressure. As a result, valuable engineering resources may need to be expended to create a satisfactory closure. Moreover, standard electrical connectors are typically not used by electrical utilities across the country. Instead, connectors may assume a variety of shapes and sizes. As the above closure may be formed in molds by injection molding, large capital investments may be required to manufacture them. Oftentimes, the ultimate market for these specialty closures may not be large enough to warrant such an investment. Furthermore, the gel may have to be placed in the closures in a discrete step, either in the manufacturing process or in the field, which may be inefficient.
U.S. Pat. No. 4,888,070 to Clark et al. proposes a flexible envelope having therein a sealing material. As noted above, gels may expand when heated causing internal stresses on the flexible envelope. If the flexible envelope is made of an elastomer having sufficient elasticity to absorb the expansion of the gel, the closure may become susceptible to splitting if placed in contact with a sharp object such as a rock. If the flexible envelope is made of a rigid material capable of withstanding such contact, the closure may become susceptible to stresses similar to those encountered by the closure, as noted above. Furthermore, the gel may typically be positioned within the flexible envelope in the field. Providing the gel in a discrete step may be inefficient.
Wrap-around cable sleeves are provided for environmentally sealing a cable section. The cable sleeves include a wrap-around body member of an electrically insulating material and have a longitudinally extending portion with a corrugated lateral cross-section. The longitudinally extending portion defines a portion of a cable chamber extending around the cable section when the body member is wrapped around the cable section. A closure edge extends along a first longitudinal edge of the body member. A sealant chamber extends along a second longitudinal edge of the body member. The sealant chamber has an opening configured to receive the closure edge when the body member is wrapped around the cable section. A sealant material is positioned in the sealant chamber to environmentally seal the longitudinal edges of the body member when the body member is wrapped around the cable section.
In other embodiments of the present invention, the cable sleeves further include a first sealant material layer on an inner face of the body member at a first end thereof that extends transversely across the first end of body member to define a continuous environmental seal between the cable section and the first end of the body member when the body member is wrapped around the cable section. A second sealant material layer may be provided on the inner face of the body member at a second end thereof, longitudinally spaced apart from the first end to define a gap portion between the sealant material layers. The second sealant material layer extends transversely substantially across the second end of body member to define a continuous environmental seal between the cable section and the second end of the body member when the body member is wrapped around the cable section. The first and second sealant material layer and the sealant material positioned in the sealant chamber, in various embodiments, sealingly contact each other when the body member is wrapped around the cable section.
In further embodiments of the present invention, the sealant chamber includes a first opening in the inner face of the body member at the first end of the body member and a second opening at the second end. The sealant material in the sealant chamber and the first sealant material layer sealingly contact each other through the first opening and the sealant material in the sealant chamber and the second sealant material layer sealingly contact each other through the second opening.
In other embodiments of the present invention, restraint members are tightened around the first end and the second end of the body member when the body member is wrapped around the cable section to place the sealant material layer under pressure in a radial direction. The body member may include a first slot in an outer face of the first end of the body member and a second slot in the outer face of the second end of the body member and the first and second restraint members may be positioned in respective ones of the slots when the body member is wrapped around the cable section.
In further embodiments of the present invention, the closure edge and the sealant chamber each include a contact surface on the inner face of the body member configured to contact the cable section to faciliate sliding thereon while the body member is wrapped around the cable section. The closure edge may also include a locking member configured to engage a mating portion of the sealant chamber to connect the closure edge and the sealant chamber when the body member is wrapped around the cable section. The longitudinally extending portion with a corrugated lateral cross-section may be a first polymer having an associated rigidity and the locking member and the mating portion of the sealant chamber may be a second polymer that provides the locking member and the mating portion of the sealant chamber a greater rigidity than the longitudinally extending portion. The first polymer may be a thermoplastic elastomer and the second polymer may be polypropylene. The body member may be co-extruded thermoplastic elastomer and polypropylene materials.
In other embodiments of the present invention, the inner face of the body member includes a gap portion between the longitudinally spaced apart first and second sealant material layers without sealant material thereon. The sealant material and the first and second sealant material layers environmentally seal the cable chamber when the body member is wrapped around the cable section. The cable chamber may have a range taking in a radial direction of at least about 15 percent and the longitudinally extending portion with a corrugated lateral cross-section may have a flexural modulus of between about 4,000 and 100,000 psi.
In further embodiments of the present invention, the sealant material and the first and second sealant material layers are a silicone gel. The closure edge is configured to place the silicone gel in the sealant chamber under compression when the body member is wrapped around the cable section and the closure edge is received in the opening of the sealant chamber.
In other embodiments of the present invention, the body member also includes a first collar portion adjacent a first end of the cable chamber and a second collar portion adjacent a second end of the cable chamber. The first and second collar portions have a range taking in a radial direction of less than 10 percent. The cable chamber may have a range taking in the longitudinal direction of less than about 10 percent. The longitudinally extending portion may have a 100% tensile modulus of between about 250 psi and 3000 psi. The longitudinally extending portion may have a tension set less than about 60 percent.
In further embodiments of the present invention, wrap-around cable sleeves are provided for environmentally sealing a cable section. A wrap-around body member of an electrically insulating material and having a longitudinally extending portion with a corrugated lateral cross-section is provided. The longitudinally extending portion defines a portion of a cable chamber extending around the cable section when the body member is wrapped around the cable section. A closure edge extends along a first longitudinal edge of the body member and a sealant chamber extends along a second longitudinal edge of the body member. The sealant chamber has an opening configured to receive the closure edge when the body member is wrapped around the cable section. A silicone gel is positioned in the sealant chamber to environmentally seal the longitudinal edges of the body member when the body member is wrapped around the cable section. The closure edge is configured to place the silicone gel in the sealant chamber under compression when the body member is wrapped around the cable section and the closure edge is received in the opening of the sealant chamber.
A first sealant material layer is positioned on an inner face of the body member at a first end thereof and extends transversely across the first end of body member to define a continuous environmental seal between the cable section and the first end of the body member when the body member is wrapped around the cable section. The first sealant material layer sealingly contacts the silicone gel in the sealant chamber. A second sealant material layer is positioned on the inner face of the body member at a second end thereof, longitudinally spaced apart from the first end to define a gap portion therebetween. The second sealant material layer extends transversely across the second end of body member to define a continuous environmental seal between the cable section and the second end of the body member when the body member is wrapped around the cable section. The second sealant material layer sealingly contacts the silicone gel in the sealant chamber.
In other embodiments of the present invention, methods are provided for forming a wrap-around cable sleeve. A web of electrically insulating material is extruded with a longitudinally extending sealant chamber therein. The web is cut to a selected length. A gel is then inserted into the sealant chamber. Gel is also applied to an inner face of the web at a first end thereof and a second end thereof. The applied gel contacts the gel in the sealant chamber at the first end and the second end to form the wrap-around cable sleeve.